Isomers of the trans-dichlorobis(2-methyl-1,2-diaminopropane) cobalt(III) cation

Abstract

Two isomers of trans-CoCl 2(ibn) 2 + have been isolated from the reaction of dioxygen with methanolic solutions of CoCl 2·6H 2O and the diamine. The most abundant is assigned the trans-gem-dimethyl configuration and the least abundant has been single crystal X-ray analysis of the ZnCl 4 2− (monohydrate) salt. Cis-gem-dimethyl- trans[CoCl 2-(ibn) 2] 2ZnCl 4·H 2O crystallizes in the monoclinic space group P2 1/ c , with a = 15.02(1), b = 11.100(2), c = 21.68(2), β = 105.64(7) and four formula units per unit cell. Each ZnCl 4 2− anion is associated with two independent cations. Both cations have the δ, λ chelate ring conformation, but differ by 3° in the ClCoCl bond angle. The rates of loss of the first chloro ligand from trans-trans- and cis-trans-CoCl 2-(ibn) 2 + were measured spectrophotometrically in 1.0 M HCI over a 15 K temperature range. At 25°C, the first order rate constant and kinetic parameters are 10 3 k (sec −1 = 0.994, 3.07, E a (kJ mol −1 = 106, 93.6, log [ PZ (sec −1] = 15.552, 13.894 and ΔS 298 ≠ J K −1 mol −1 = +44.5, +12.8 respectively.